Rear-end collision is a significant category of crashes, accounting for nearly one in four of all collisions, or 1.7 million total crashes, in 1998 alone, according to U.S. Department of Transportation (DOT) statistics. Rear-end collisions result in approximately 2,000 deaths, or approximately 4.5% of all traffic related deaths, and approximately 950,000 injuries annually. Rear-end collisions are generally characterized as either “lead vehicle stationary” or “lead vehicle moving.” The incidence of lead vehicle being stationary occurs at least twice as often as a moving lead vehicle.
The most prevalent existing rear-end collision prevention mechanism is a plurality of red brake lights positioned so as to face the rear direction of a lead vehicle, which activate so that the red brake lights are constantly illuminated when a driver of the lead vehicle is depressing a brake pedal of the lead vehicle. These red brake lights, when activated, help drivers following the lead vehicle to determine whether the lead vehicle is reducing speed or stopping. However, despite of the use of such red brake lights, rear-end accidents still occur.
In an attempt to prevent or minimize damage and injury caused by traffic collisions, various systems have been previously developed. U.S. Pat. No. 5,786,752 entitled “Emergency Signal System For Vehicles” describes a warning system provided on a lead vehicle having at least one light emitting signal facing rearward, a velocity measurement sensor for measuring an absolute velocity of the lead vehicle and a control unit coupled to the velocity measurement sensor for determining if the measured absolute velocity is greater than a threshold velocity. A warning is transmitted to vehicles approaching from the rear when a velocity of the lead vehicle is below the threshold velocity.
U.S. Pat. No. 6,225,896 entitled “Panic Stop, Deceleration Warning System” describes a rear-end warning system that uses a lead vehicle's standard white reverse light in addition to the red brake lights.
U.S. Pat. No. 6,359,552 entitled “Fast Braking Warning System” discloses a collision warning system that warns vehicles traveling behind a lead vehicle when the lead vehicle initiates deceleration. The disclosed system has two modes of warning operation, initiate warn and repeat warn. In the first mode, a lead vehicle initiating a sudden deceleration detects its own slowdown and transmits a warning to the rear of the vehicle. The second mode of operation does not detect deceleration of the lead vehicle, but instead receives a transmitted warning from the vehicle(s) ahead of the lead vehicle and automatically actuates the lead vehicle's red brake lights. The warning is also simultaneously retransmitting to the rear to actuate the brake lights of the next vehicle.
U.S. Pat. No. 6,012,008 entitled “Method and Apparatus for Predicting A Crash And Reacting Thereto” discloses an active sensing system for predicting a collision. The sensing is based on reflection of pulse signals (e.g., radar, laser) and measuring “time-of-flight” thereof.
U.S. Pat. No. 6,213,512 entitled “Seat Belt Tightening Apparatus” and U.S. Pat. No. 6,746,049 entitled “Adaptive Seat Belt Tensioning System” describe two systems for controlling seat belts and tension during operation of a lead vehicle.
U.S. Pat. No. 6,571,161 entitled “Pre-crash Assessment of Crash Severity for Road Vehicles” discloses a method for predicting the severity of an imminent crash of road vehicles using a sensor, a computer system coupled with pre-crash vehicle condition signal sources and a vehicle communication system onboard each of two vehicles involved in a crash. The method includes the steps of determining that a collision of the vehicles is imminent, exchanging vehicle crash-related information between the vehicles when an imminent collision is determined, computing crash-defining information onboard each vehicle and predicting onboard each vehicle the severity of the imminent collision, whereby occupant protection devices of the vehicles may be deployed in accordance with the predicted severity.
In other approaches, The Insurance Corporation of British Columbia (ICBC), through its road improvement program, has been funding road improvements in order to reduce the frequency of collisions at high crash locations in British Columbia. Several road safety engineering countermeasures specifically targeted at rear end collisions have been researched and deployed. These countermeasures include simple and affordable solutions such as signal visibility enhancements, as well as complex and expensive solutions such as intersection geometric upgrades. When appropriately used, these countermeasures have proven to be extremely cost-effective in reducing the frequency of rear end collisions. Widespread application of signal visibility enhancements is now being pursued to further decrease the risk of rear end collisions and whiplash injuries.
Most current approaches by the U.S. DOT Institute of Traffic Safety (ITS) to the rear-ending problem involve frontal collision warning systems that involve forward radar and/or vision sensors that detect the relative speed to the vehicle or object in the front and give a warning if there is a danger of collision. The ITS web site generally describes certain concepts employing a rear signal light that activates when a rear-facing sensor detects an imminent collision. The idea is to attract the following driver's attention and signal him/her that quick and forceful braking or steering is necessary to avoid a rear-end crash with the lead vehicle. Another related ITS concept, entitled “Rear Impact Collision Warning System” transmits a warning from a bus to a driver of a vehicle directly behind the bus about a potential collision.
In additional efforts, the ANN ARBOR TRANSPORTATION AUTHORITY and VERIDIAN ENGINEERING have announced significant progress in determining factors that cause rear impact collisions. They are now studying lighting options for the warning display for the back of the buses. This initiative is being coordinated with the National Highway Traffic Safety Administration's Enhanced Rear Signaling Systems project.
The existing collision warning systems focus mainly on detecting potential collision and pre-arming devices such as air-bags and seat belts. Such systems do not generally address warning a driver of a vehicle about to be impacted. Accordingly, there is a need for a method and apparatus for rear-end collision warning and accident mitigation that addresses certain limitations found in existing technologies.